class Shard {
    constructor(x, y, hue) {
        this.x = x;
        this.y = y;
        this.hue = hue;
        this.lightness = 50;
        this.size = 15 + Math.random() * 10;
        const angle = Math.random() * 2 * Math.PI;
        const blastSpeed = 1 + Math.random() * 6;
        this.xSpeed = Math.cos(angle) * blastSpeed;
        this.ySpeed = Math.sin(angle) * blastSpeed;
        this.target = getTarget();
        this.ttl = 100;
        this.timer = 0;
    }

    draw() {
        ctx2.fillStyle = `hsl(${this.hue}, 100%, ${this.lightness}%)`;
        ctx2.beginPath();
        ctx2.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
        ctx2.closePath();
        ctx2.fill();
    }

    update() {
        if (this.target) {
            const dx = this.target.x - this.x;
            const dy = this.target.y - this.y;
            const dist = Math.sqrt(dx * dx + dy * dy);
            const a = Math.atan2(dy, dx);
            const tx = Math.cos(a) * 5;
            const ty = Math.sin(a) * 5;
            this.size = lerp(this.size, 1.5, 0.05);

            if (dist < 5) {
                this.lightness = lerp(this.lightness, 100, 0.01);
                this.xSpeed = this.ySpeed = 0;
                this.x = lerp(this.x, this.target.x + fidelity / 2, 0.05);
                this.y = lerp(this.y, this.target.y + fidelity / 2, 0.05);
                this.timer += 1;
            } else if (dist < 10) {
                this.lightness = lerp(this.lightness, 100, 0.01);
                this.xSpeed = lerp(this.xSpeed, tx, 0.1);
                this.ySpeed = lerp(this.ySpeed, ty, 0.1);
                this.timer += 1;
            } else {
                this.xSpeed = lerp(this.xSpeed, tx, 0.02);
                this.ySpeed = lerp(this.ySpeed, ty, 0.02);
            }
        } else {
            this.ySpeed += 0.05;
            //this.xSpeed = lerp(this.xSpeed, 0, 0.1);
            this.size = lerp(this.size, 1, 0.05);

            if (this.y > c2.height) {
                shards.forEach((shard, idx) => {
                    if (shard === this) {
                        shards.splice(idx, 1);
                    }
                });
            }
        }
        this.x = this.x + this.xSpeed;
        this.y = this.y + this.ySpeed;
    }
}


class Rocket {
    constructor() {
        const quarterW = c2.width / 4;
        this.x = quarterW + Math.random() * (c2.width - quarterW);
        this.y = c2.height - 15;
        this.angle = Math.random() * Math.PI / 4 - Math.PI / 6;
        this.blastSpeed = 6 + Math.random() * 7;
        this.shardCount = 15 + Math.floor(Math.random() * 15);
        this.xSpeed = Math.sin(this.angle) * this.blastSpeed;
        this.ySpeed = -Math.cos(this.angle) * this.blastSpeed;
        this.hue = Math.floor(Math.random() * 360);
        this.trail = [];
    }

    draw() {
        ctx2.save();
        ctx2.translate(this.x, this.y);
        ctx2.rotate(Math.atan2(this.ySpeed, this.xSpeed) + Math.PI / 2);
        ctx2.fillStyle = `hsl(${this.hue}, 100%, 50%)`;
        ctx2.fillRect(0, 0, 5, 15);
        ctx2.restore();
    }

    update() {
        this.x = this.x + this.xSpeed;
        this.y = this.y + this.ySpeed;
        this.ySpeed += 0.1;
    }

    explode() {
        for (let i = 0; i < 70; i++) {
            shards.push(new Shard(this.x, this.y, this.hue));
        }
    }
}


// init
const [c1, c2, c3] = document.querySelectorAll('canvas');
const [ctx1, ctx2, ctx3] = [c1, c2, c3].map(c => c.getContext('2d'));
let fontSize = 200;
const rockets = [];
const shards = [];
const targets = [];
const fidelity = 3;
let counter = 0;
c2.width = c3.width = window.innerWidth;
c2.height = c3.height = window.innerHeight;
ctx1.fillStyle = '#000';
const text = '胖不了小陆';
let textWidth = 99999999;

while (textWidth > window.innerWidth) {
    ctx1.font = `900 ${fontSize--}px Arial`;
    textWidth = ctx1.measureText(text).width;
}

c1.width = textWidth;
c1.height = fontSize * 1.5;
ctx1.font = `900 ${fontSize}px Arial`;
ctx1.fillText(text, 0, fontSize);
const imgData = ctx1.getImageData(0, 0, c1.width, c1.height);
for (let i = 0, max = imgData.data.length; i < max; i += 4) {
    const alpha = imgData.data[i + 3];
    const x = Math.floor(i / 4) % imgData.width;
    const y = Math.floor(i / 4 / imgData.width);

    if (alpha && x % fidelity === 0 && y % fidelity === 0) {
        targets.push({x, y});
    }
}

ctx3.fillStyle = '#FFF';
ctx3.shadowColor = '#FFF';
ctx3.shadowBlur = 25;

// ANIMATION LOOP
(function loop() {
    ctx2.fillStyle = "rgba(0, 0, 0, .1)";
    ctx2.fillRect(0, 0, c2.width, c2.height);
    // ctx2.clearRect(0, 0, c2.width, c2.height);
    counter += 1;

    if (counter % 15 === 0) {
        rockets.push(new Rocket());
    }
    rockets.forEach((r, i) => {
        r.draw();
        r.update();
        if (r.ySpeed > 0) {
            r.explode();
            rockets.splice(i, 1);
        }
    });

    shards.forEach((s, i) => {
        s.draw();
        s.update();

        if (s.timer >= s.ttl || s.lightness >= 99) {
            ctx3.fillRect(s.target.x, s.target.y, fidelity + 1, fidelity + 1);
            shards.splice(i, 1);
        }
    });

    requestAnimationFrame(loop);
})();

// HELPER FUNCTIONS
const lerp = (a, b, t) => Math.abs(b - a) > 0.1 ? a + t * (b - a) : b;

function getTarget() {
    if (targets.length > 0) {
        const idx = Math.floor(Math.random() * targets.length);
        let {x, y} = targets[idx];
        targets.splice(idx, 1);

        x += c2.width / 2 - textWidth / 2;
        y += c2.height / 2 - fontSize / 2;

        return {x, y};
    }
}
